In the absence of high-quality biodiversity data, land-use planners and conservationists often rely on biodiversity surrogates (Margules and Pressey 2000; Pinto et al. 2008). In the tropics, where endemic species are common and little information is available regarding the life history and ecology of most taxa, the surrogate approach has been recommended, even for relatively species-poor communities and relatively small areas (Wiens et al. 2008). However, studies often propose surrogates without considering who will use them and why they are better than direct measures (Caro 2010).
Biodiversity surrogates require a trade-off between the surrogates’ ability to reflect the distribution of unsampled species and the cost of sampling species in the field (Gardner et al. 2008; Lansac-Tôha et al. 2022). This approach has been applied to numerous taxonomic groups in terrestrial (Corcos et al. 2021; Verdinelli et al. 2022) and aquatic ecosystems (Pakulnicka et al. 2015; Spigoloni et al. 2022). If a surrogate is identified, the results could be utilized to prioritize locations or actions for conservation purposes (Nogueira et al. 2023). However, evaluating the effectiveness of surrogates in conservation planning is challenging (Fattorini et al. 2012; Covre et al. 2022) since it necessitates the availability of the same extensive datasets whose absence initially justified the use of surrogates.
In cases where surrogates appear to underestimate complementarity, assessing the effectiveness of frequently used surrogates or establishing new ones may be necessary. In the Amazon, data on the distributions of various taxonomic groups are still too incomplete to serve as the foundation for systematic conservation planning (Brasil 2008). As a result, conservation targets aiming to maximize complementarity between protected areas have been established based on untested assumptions about the environmental niches of most species. These targets typically rely on ecoregions, vegetation types, and soil types as biodiversity surrogates (Peres 2005). However, the use of general classifications, such as broadscale environmental data, is not always useful because biological processes and ecological interactions can operate at different scales due to the non-uniform geographical distribution of environmental conditions (McGill 2010; Lu and Jetz 2023). Moreover, relying solely on broadscale environmental data may obscure important relationships between species and their environment (Qian and Kissling 2010; Monteiro et al. 2023)
This appears to be the case for the interfluve Purus-Madeira located in southwestern Amazonia; a large forested area, 800 km in extent where maps of vegetation types and geology show a relatively homogeneous landscape (Brasil 2008). However, biological surveys have revealed compositional heterogeneity across the region (Baccaro et al. 2013; Marciente et al. 2015; Schietti et al. 2016; Peixoto et al. 2019; Stegmann et al. 2019; Salomão et al. 2022).
Due to the inconsistent conclusions regarding the effectiveness of using broadscale environmental data in a large forested area as biodiversity surrogates in the Amazon and potentially in other parts of the world, it becomes necessary to identify alternative effective biodiversity surrogates that can support conservation efforts. One potential alternative is considering the biotic interactions between taxonomic groups (Cosentino et al. 2023; Bazzato et al. 2023).
For example, birds interact with palm species in various ways, utilizing them as food resources, nesting, roosting and perching sites (Snow 1981; Brightsmith and Cáceres 2017; van der Hoek et al. 2019; Glória and Tozetti 2021). The extent to which birds exploit different plant species depends on their specific characteristics, such as whether they are canopy or understory birds (Bradfer-Lawrence et al. 2018; LIMA et al. 2023). On the other hand, the composition of palm species changes in response to environmental variation (Sousa et al. 2020; Muscarella et al. 2020), with some species showing strict associations with specific environmental characteristics. For instance, the presence of Oenocarpus bacaba palm species indicates well-drained soils (Cohn-Haft et al. 2007), while Lepidocaryum tenue is more commonly found in wet conditions (Cohn-Haft et al. 2007).
Land-use planning is not only a central-government activity. Citizen scientists are often involved in data acquisition and subsequent planning (Garretson et al. 2023; Jesus et al. 2023), but they often do not have the experience to sample assemblages potentially consisting of hundreds of species. Involvement of local communities is facilitated if they can initially focus on species with which they are already familiar and use as resources, such as the palm species.
In this scenario, if biotic interactions between birds and palms are significant, it would be expected that changes in bird species composition are related to corresponding shifts in the abundance of palm species. If such a relationship is found, palm species, which are sedentary and potentially much easier to sample, could potentially serve as effective biodiversity surrogates for birds. To assess the potential to use data on palms as a substitute for bird assemblages, we compared the relationship between the distribution of 26 bird species from different taxonomic groups with the distribution of the five most abundant palm species along the interfluve Purus-Madeira (Lepidocaryum tenue, Attalea speciosa, Mauritiella aculeata, Oenocarpus bataua, Oenocarpus bacaba), the environmental factors that commonly affect species distributions in that region (Precipitation, Water-table levels, Sand and Clay content), and the ecoregions proposed by (Ximenes 2008), who considered the region to be relatively heterogeneous. If bird-assemblage composition is more strongly correlated with changes in palm-species abundance, palms could serve as a cost-effective and efficient biodiversity surrogate for birds in this region. Moreover, these palm species are abundant in the region and can be easily identified and monitored by non-specialists, such as those in local communities.